Fuel stoker



y 24, 1938- CPSCHOLL 2,118,625

FUEL STOKER Filed Oct. 8, 1934 4 Sheets-Sheet 1 TN VENTOQ CZar/r 56/2 0 it a ?M4M/x% (ATTORNEYS May 24, 1938.

c. SCHOLL FUEL ,STOKER Filed Oct. 8, 1934 4 Sheets-Sheet 2 9 1 0/ N T w M p\ N/ 0 Wi I 1 l l I v. r

c. scHoLL FUEL ,STOKER Filed Oct. 8; 1934 4 Sheets-Sheet 5' UN VEZNTOQ a h c 6 m m 0 c. SCHQLL FUEL STOKER May 24, 1938.

Filed Oct. 8, 1954 4 Sheets-Sheet 4 QTTO NELYS IN VETNTOQ (la/k LSb/woll III Patented May 24, 1938 PATENT OFFICE FUEL STOKER Clark Scholl, Springfield, Ohio,

assignor, by

mesne assignments, to The Steel Products Engineering Company, Springfield, Ohio, a corporation of Ohio Application October 8,

' 12 Claims.

The present invention relates to improvements in fuel stokers of the underfeed type, and more particularly to a novel method and means for preventing the escape of smoke and obnoxious gases to the surrounding atmosphere.

Underfeed stokers ordinarily comprise a fuel hopper, a burner adapted to be mounted in a closed combustion chamber and having an upwardly opening retort with tuyere openings adjacent the top and a plenum chamber about the retort and communicatingwith the tuyere openings, a duct connecting the hopper and the retort, conveyer means for feeding fuel through the duct toward the retort, an air duct connected to the plenum chamber, and means for supplying air under pressure to the air duct. The pressure of the air at the zone of combustion tends to force some smoke and products of distillation and combustion backwardly through the duct and hopper into the surrounding atmosphere. This is objectionable in that it reduces the efficiency of combustion, and. results in an unclean and unhealthful condition which is particularly offensive in domestic installations.

It has been proposed heretofore to overcome the foregoing diiliculty by introducing air under pressure from the air duct or the plenum chamber into the fuel duct. The air so introduced was intended to counterbalance the downward pressure in the retort. It has been found, however, that under many operating conditions, such counterbalancing of pressures effective to prevent objectionable back smoking and gassing is not obtained. Where the air is introduced through long or restricted passages, the pressure is likely to suffer a substantial dropbefore'entering the duct to a point below that at the zone of combustion. Moreover, the air can reach the combustion chamber only by passing upwardly through the compact fuel bed which sets up a substantial resistance to flow, and hence still further decreases the counter-pressure. Since the fuel rarely fills the duct completely but defines an unrestricted air passage along the top to the hopper when a conveyer screw is employed, the resistance to upward flow tends to cause a substantial portion' of the air with smokeand obnoxious gases to pass to the hopper. This is particularly true where certain kinds of cheap fuel are used.

The primary object of the present invention therefore resides in the use of a novel means for preventing back smoking and gassing by scavenging the fuel duct of smoke and obnoxious gases that may pass downwardly from the zone of combustion, and preferably returning such smoke and 1934, Serial No. 747,327

ases to the combustion chamber without requiring them to pass through the fuel bed.

Another object resides in the provision of an underfeed stoker comprising new and improved means in the form of a relatively short and low resistance air flow passage from the source of pressure air through the upper portion of the fuel duct directly to the zone of combustion.

Further objects reside in the provision of a novel means in the form of a low resistance air flow passage including the duct for preventing back smoking and gassing which is eflicient in operation, and simple, compact and inexpensive in construction.

Other objects and advantages will become apparent as the description proceeds.

In the accompanying drawings, Figure l is a plan view of a stoker embodying the features of my invention.

Fig. 2 is a fragmentary plan view on an enlarged scale of the base section of the burner.

Fig. 3 is a longitudinal vertical sectional view taken along line 3-3 of Fig. 2, but with tuyre blocks mounted on the burner base section.

Fig. 4 is an elevational view of the inlet end of the burner.

Figs. 5 and 6 are fragmentary transverse sectional views taken respectively along lines 5-5 and 6--6 of Fig. 2.

Fig. '7 is a fragmentary sectional view taken in the plane of Fig. 3, but illustrating a modified form of the invention.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawings, the stoker constituting the preferred embodiment of the invention comprises an upright fuel hopper I0, an underfeed burner H, a fuel duct i2 connecting the base of the hopper. to the burner, a screw conveyer [3 extending from the hopper into the duct for feeding fuel to the burner, and power drive means it for rotating the conveyer.

The burner ll may be provided in various forms, and is herein shown as comprising a base section [4 generally rectangular in form and adapted t b mounted on a suitable support (notshown). The base section I4 has an upright wall I5 and top and bottom walls I6 and I1. Formed integral with the base section I4 is a retort I8 opening upwardly through the central portion of the wall I6 and having a horizontal cylindrical inlet duct 'or passage I9 opening through the wall I5 at the front end of the burner II.

Formed on the exterior of the wall I5 in axial alignment with the duct I9 is a mounting ring 20 snugly receiving the discharge end of the duct I 2. A semi-cylindrical bracket 2I with marginal side flanges 22 is formed integral with the upper portion of the ring 20, and constitutes an axial extension thereof. The fuel duct I2 is securely clamped in position between the bracket 2| and an underlying semi-cylindrical plate 23 abutting against the end of the ring 20 and having marginal side flanges 24 bolted to the flanges 22. A pin 25 extends vertically through the bottom of the plate 23 into a hole 26 in the duct I2 to hold the latter against rotation.

The base section I4,defines a plenum chamber 21 about the retort I 8. A blower 28, mounted in fixed relation to the hopper III and operatively connected to the drive means I3 discharges through an air duct 29 to the chamber 21.

Mounted on the top wall I6 of the base section I4 and about the upper edge of the retort I8 to constitute a vertical continuation thereof are a plurality of closely abutting tuyere blocks 30 and two front tuyere blocks 30 The blocks 30 when assembled define an air chamber 3i communicat ing through openings 32 in the bottom Walls of the blocks and registering openings 33 in the top wall IS with the plenum chamber 21, and discharging through tuyre openings 34 to the pace immediately above the retort I8.

In operation, fuel from the hopper I0 is ed through the duct I2 into the retort I8 in which it is forced upwardly to form the fuel bed. Air under pressure from the chamber 2'1 is discharged through the openings 33 and 32, the chamber 3| and the tuyere openings 34 into the top of the bed to support combustion. As combustion occurs, the pressure created at the zone of combustion by the pressure of the air tends to force some of the products of combustion and the products of initial distillation obtained in the lower portion of the retort l8 into the fuel duct I2.

The primary feature of the present invention resides in effectively preventing such products from passing backwardly to the hopper Ill, and

more particularly in removing them from the tube I 2. The means employed for this purpose serves to effect the flow of a constant stream of air under pressure through the discharge end of the duct I2 and then outwardly along a path of low resistance. Any smoke or obnoxious gases entering the duct l2 become entrained in the air and are therefore removed before they can reach the hopper I0. In addition, the air intro duced into the duct I2 sets up a pressure in opposition to the back pressure in the retort I8, and to the extent that this is effective serves to reduce the amount of the objectionable products to be removed.

In the present instance, the means for preventing back smoking and gassing comprises an external hollow T-shaped enlargement 35 formed on the top of the bracket 2I and defining a similarly shaped air passage 36. The lateral ends of the passage 36 are connected respectively through openings 37 in the wall IE to the plenum chamber 21. The longitudinal end of the passage 36 discharges laterally through an opening 38 to the inner surface of the bracket 2|. Two parallel longitudinal slots 39 are formed in and open through the top portion of the duct I2, and are in registration with the opening 38 to complete the air passage connection between the plenum chamber 21 and the'duct.

The two front tuyere blocks 30, adjacent the inlet end of the burner II, define an air chamber 40 with a tuyre opening 4| and out of direct communication with the plenum chamber 21. These blocks rest on a connecting portion 42 of the top wall I6 between the wall I5 and the retort I8. Two depending T-shaped lugs 44 on the front tuyre blocks 30 fit respectively in notches 45 in opposite sides of the wall portion 42, and the heads of the lugs hook under the marginal edges thereof. Two parallel spaced vertical walls 46 extending downwardly from the wall portion 42 to the duct I 9 between the wall I5 and the retort I8 define with these parts an air chamber 41 which communicates at the top through an opening 48 in the wall portion 42 with the chamber 40 and through an opening 49 in the front Wall of the retort IS with the interior of the latter adjacent the top of the duct I9. Extending downwardly and forwardly in the chamber 4'! from the upper edge of the retort I3 partially across the opening 49 is an inclined baffle Wall 59.

During the operation of the stoker, air under pressure from the plenum chamber 2? passes through the openings ill, the passage 36, the opening 38 and the slots 39 into the upper por tion of the discharge duct I2. The connection is comparatively short and substantially unrestricted, and hence the pressure of the air entering theduct I2 is practically the same as that of the air entering the fuel bed at the zone of combustion through the tuyre openings 34. The pressure in the duct I2 opposes the downward air pressure in the retort I8, and therefore tends to reduce the quantity of smoke and gases that may seek an outlet through the hopper I0. The air passes over the fuel between the slots 39 and the discharge end of the duct I2 and duct I9, through the opening 49, and across the bafiie wall 50 into the chamber 41, and then through the opening 48, the chamber 40 and the tuyre opening 4i into the fuel bed at the Zone of combustion. Thus, the air flows in contact with the fuel along a short path of comparatively low resistance. Unless the stoker is operating at full load, there is likely to be an air space in the top of the duct I2 adjacent its discharge end. In this case, a part of the air introduced through the slots 39 will flow through this unrestricted opening and out through the opening 49. However, the direct connection between the plenum chamber 21 and 'the duct I2 by way of the passage 36 will provide for the flow of a sufficient volume of air to permeate the mass of fuel in the lower part of the duct and effectually prevent smoke and gases from passing back through the duct to the hopper Ill. The air is not obliged to pass through the .relatively large mass of fuel in the fire bed but takes the path of lower resistance through the openings 49 and 4|. The air will not flow backwardly through the loaded hopper I2 since the above described path is the one of least resistance. Thus, there will be a current of air flowing through the duct I2 in a direction away from the hopper I0, and this current of air will entrain any smoke or obnoxious gases that may be present. As a result, back smoking and gasing is effectively prevented.

In the modified form shown in Fig. 7, the duct H3 extends externally of the vertical wall of the base section and is formed with a long counterbore 52 receiving the discharge end of the duct l2. The base section is formed with an air chamber 53 which communicates upwardly through an opening 54 in the wall Ili with the interior of the tuyre structure and downwardly through an opening 55 with the interior of the duct IS. A slot 56, formed in the top of the duct l2 and inclined downwardly and rearwardly, registers with the opening 55 to complete the air flow connection between the plenum chamber 21 and the duct. A discharge pipe'5'l, connected to the duct I9 communicates, through notches 5B and 59 formed respectively in the end of the duct M and the shoulder defined by the counterbore 52, with the retort IB and extendsupwardly through the chamber 53, the opening 54 and the tuyre' structure. The pipe 51 may lead to any suitable place of disposal for the air and entrained products entering from the duct l2, and is herein shown as discharging through one of the tuyere openings 34 to the zone of combustion. The operation is similar to that of the form illustrated in Figs. 1 to 6.

I claim as my invention:

1. A stoker comprising, in combination, an

underfeed burner having a retort, a tuyre structure on said retort, and a plenum chamber about said retort and communicating with said tuyere structure, a hopper, a horizontal duct connecting said hopper to said retort, a conveyer for advancing fuel from said hopper through said duct into said retort, means for supplying air under pressure to said plenum chamber, a semi-cylindrical bracket on said burner and engaging the upper portion of the discharge end of said duct, a complementary semi-cylindrical plate removably secured to said bracket and engaging the underside of said duct, a longitudinal slot formed in the top and opening through the wall of said duct, an air flow passage formed in said bracket and communicating at spaced points with said plenum chamber and communicating through said slot with the interior of said duct, means defining an auxiliary tuyere chamber out of direct communication with said plenum chamber, and having an inlet opening from said retort adjacent the upper portion of the discharge end of said duct, and a downwardly inclined depending baflle in said auxiliary chamber extending across said inlet.

2. A stoker comprising, in combination, an underfeed burner having a retort, a tuyere structure on said retort and a plenum chamber about said retort and communicating with said tuyre structure, a hopper, a horizontal duct connecting said hopper to said retort, a conveyer for advancing fuel from said hopper through said duct into said retort, means for supplying air under pressure to said plenum chamber, a bracket on said burner and engaging the upper portion of the discharge end of said duct, means for securing said duct in position against the underside of said bracket, an opening in the top wall of said duct, an air flow passage formed in said bracket and communicating with said plenum chamber and through said opening with. the interior of said duct, and means defining an auxiliary tuyre chamber out of direct communication with said Plenum chamber, and having an inlet opening from said retort adjacent the upper portion of the discharge end of said duct.

3. In a stoker, in combination, a burner having an underfecd retort and a tuyre structure on said retort and including a tuyere chamber and an auxiliary tuyere chamber, a fuel duct discharging into the bottom of said retort,. means for supplying air under pressure to said duct, and means providing an -air passage connecting the interior of said retort to said auxiliary tuyre chamber and utilizing the pressure of theair supplied to said duct for returning gases from said duct and from the lower portion of the retort through the tuyere structure to the upper portion of the retort.

4. In a stoker, in combination, a burner having an underfeed retort anda tuyere structure on said retort and including a tuyre chamber and an auxiliary tuyre chamber, a fuel duct discharging into the bottom of said retort, means for supplying air under pressure to said duct, and means providing an air passage connecting the interior of said retort adjacent the discharge end of said duct to said auxiliary tuyre chamber and utilizing the pressure of the air supplied to said duct for returning gases from said duct and from the lower portion of the retort through the tuyere structure to the upper portion of the retort.

5. In a stoker, in combination, a burner having an upwardly opening underfeed retort with a horizontal fuel inlet duct, and a tuyere structure on said retort having a tuyre chamber and an auxiliary tuyre chamber out of direct communication with said tuyre chamber, a fuel duct discharging into said inlet duct, means for'supplying air under pressure to the upper portion of the discharge end of said fuel duct, and means providing an air passage and utilizing the pressure of the air supplied to said fuel duct for returning gases from said fuel duct and from the lower portion of said retort through said tuyere structure to the upper portion of said-retort, said air passage connecting the interior of said retort adjacent the point of juncture with the top of said inlet duct directly to said auxiliary tuyere chamber.

6. In a stoker, in combination, a burner having an underfeed retort with a horizontal inlet duct, means for supplying fuel to said duct, means for supplying air under pressure through said duct into said retort, and means forming an air outlet from said retort at a point adjacent the outlet of said duct and utilizing the pressure of the air supplied through said duct to said retort for scavenging gases from the lower portion of the retort.

'7. In a stoker, in combination, a burner having an upwardly opening underfeed retort, means for supplying fuel to the bottom of said retort, means for admitting air under pressure to the lower portion of said retort, means for withdrawing air and gases from the lower portion of said retort, and means including a by-pass located outside said retort for returning said air and gases to the upper portion of said burner.

8. In a stoker, in combination, a burner having an upwardly opening underfeed retort, means for supplying fuel to the bottom of said retort, a tuyere structure on said retort, means for admitting air under presure to the lower portion of said retort, and means for withdrawing air from the lower portion of said retort and directing same to said tuyre structure to be discharged into the top of said burner.

-9. In a stoker, in combination, a burner having an upwardly opening under feed retort, means for supplying fuel to the bottom of said retort, a tuyere structure on said retort and having a discharge op ning, means for admitting air under pressure to the lower portion of said retort, and a pipe opening from the lower portion of said retort, and discharging to said discharge opening of said tuyere structure.

10. A stoker comprising, in combination, an underfeed burner having a retort with a horizontal inlet duct, a main tuyere structure, an auxiliary tuyre structure, said structures being disposed on said retort, and a plenum chamber about said retort and communicating with said main tuyere structure, a hopper, a horizontal fuel duct connecting said hopper to said inlet duct, 9. conveyer for advancing fuel from said hopper through said ducts into said retort, means for supplying air under pressure to said plenum chamber, a bracket on said burner and engaging the upper portion of the discharge end of said fuel duct, a plate removably secured to said bracket and engaging the underside of said fuel duct, a slot formed in the top of said fuel duct, an air flow passage formed in said bracket and connected to said plenum chamber and through said slot with the interior of said fuel duct, an opening formed in said retort below said main tuyere structure and communicating through a passage directly with said auxiliary tuyre structure.

11. A stoker comprising, in combination, an

underfeed burner having an upwardly opening retort, a tuye're structure mounted on the top of said retort and coacting with said retort to define a fire pot, means for supplying air under pressure to said tuyre structure, a substantially horizontal fuel supply duct means opening to the bottom of said retort and formed in the top with longitudinally spaced air inlet and outlet openings, a passage connecting said air supply means to said inlet opening, and a passage for conducting gases away from said outlet opening.

12. A stoker comprising, in combination, an underieed burner having an upwardly opening retort, a tuyre structure mounted on the top of said retort and coacting with said retort to define a fire pot, means for supplying air under pressure to said tuyre structure, a substantially horizontal fuel supply duct means opening to the bottom of said retort and formed in the top with an air inlet opening spaced from said fire pot and an air outlet opening at the lower portion of said fire pot, a passage connecting said air supply means to said inlet opening and a passage formed in part by said tuyre structure for directing air and gases from said outlet opening to the top of said fire pot.

CLARK SCHOLL. 

